The present invention concerns a catalyst for polymerizing .alpha.-olefins and to a process for polymerizing .alpha.-olefins. The resultant polymers have relatively narrow molecular weight distributions.
Lowery, Jr. et al in U.S. Pat. No. 4,250,288, U.S. Pat. No. 4,319,011, and Coleman III, et al in U.S. Pat. No. 4,452,914 disclose high efficiency magnesium halide supported Ziegler Natta catalysts for polymerizing .alpha.-olefins. While the resultant polymers are highly useful, it would be desirable if the molecular weight distribution of such polymers were narrowed somewhat so as to result in polymers for film applications with improved clarity and toughness. The present invention provides a method for narrowing the molecular weight distribution of polymers prepared with the Lowery et al and similar catalysts.